Lutein to zeaxanthin isomerization process and product

Abstract

A lutein to zeaxanthin isomerization process which includes a saponification or alkali treatment of a plant extract containing lutein followed by a heating period under controlled conditions, is carried out in the presence of a surface active agent having an HLB of from 1 to 40 as a catalyst for the lutein to zeaxanthin isomerization reaction, at a temperature between 70 to 140° C., in order to obtain a reaction product with high zeaxanthin concentrations of up to 80% of the total carotenoids.

What is claimed is:  
     
       1. A lutein to zeaxanthin isomerization process comprising the saponification or alkali treatment of a plant extract containing lutein, followed by a heating period, wherein the saponification or alkali treatment and heating period are carried out in the presence of a catalyst for the lutein to zeaxanthin isomerization reaction and at a temperature of from about 60 to 140° C., thus obtaining an approximate yield of 25 to 96% of conversion of the lutein contained in the plant extract, the catalyst being a surfactant which is suitable for use in food or feed additives and which has a Hydrophile-Lipophile Balance of between 1 and 40, wherein the catalyst is selected from the group consisting of propylene glycol, keto-stearyl 20-POE alcohol, ethylene glycol distearate, ammonium lauryl sulfate, sodium lauryl sulfate, triethanol amide lauryl sulfate, alkyl benzene sodium sulfonate, polyglycolic esters of fatty acids, nonyl phenol 30-POE, polyethylene glycol distearate, sorbitan monostearate 20-POE, sorbitan mono oleate 20-POE, or mixtures thereof. 
     
     
       2. A lutein to zeaxanthin isomerization process according to  claim 1 , wherein the surfactant is present in a proportion of from about 1 to 35% by weight of the plant extract containing lutein. 
     
     
       3. A lutein to zeaxanthin isomerization process according to  claim 2 , wherein the plant extract containing lutein is selected from an extract of marigold flower, alfalfa, chilli and any other plant variety containing carotenoids. 
     
     
       4. A lutein to zeaxanthin isomerization process according to  claim 3 , wherein the plant extract containing lutein is marigold flower extract and the amount of surfactant employed is from about 5 to 15% by weight of the plant extract containing lutein. 
     
     
       5. A lutein to zeaxanthin isomerization process according to  claim 2 , wherein the saponification or alkali treatment is carried out by treating the plant extract containing lutein with an aqueous solution of an alkali selected from sodium hydroxide, potassium hydroxide, calcium hydroxide or mixtures thereof, at a temperature approximately between 60 and 140° C.; and the heating period is carried out at a temperature of approximately between 60 and 140° C. 
     
     
       6. A lutein to zeaxanthin isomerization process according to  claim 2 , wherein the saponification or alkali treatment is carried out by treating the plant extract containing lutein with an alcoholic solution of an alkali selected from sodium hydroxide, potassium hydroxide, calcium hydroxide or mixtures thereof. 
     
     
       7. A lutein to zeaxanthin isomerization process according to  claim 6 , wherein the alcoholic solution is prepared with a low molecular weight alcohol selected from methanol, ethanol, isopropyl alcohol and mixtures thereof. 
     
     
       8. A lutein to zeaxanthin isomerization process according to  claim 5 , wherein the plant extract containing lutein is marigold flower extract; the saponification reaction is carried out by using an aqueous solution of potassium hydroxide with a concentration of from about 20 to 70% by weight, at a temperature of 110 to 120° C. and at atmospheric pressure; and the heating period is carried out at a temperature of between 70 to 140° C., during 60 to 90 minutes, approximately, thus obtaining a reaction product containing up to approximately 80% of zeaxanthin of the total carotenoids. 
     
     
       9. A lutein to zeaxanthin isomerization process according to  claim 8  wherein the saponification reaction is carried out by using an aqueous solution of potassium hydroxide with a concentration of about 50% by weight. 
     
     
       10. A lutein to zeaxanthin isomerization process according to  claim 8  wherein an additional mixing step is performed by mixing the reaction product with a pigmenting composition having low zeaxanthin concentration, in order to obtain a pigmenting composition which is stable in respect to the total carotenoid concentration for long periods of time.